## Why
Second pass at the complexity report. After the trial-experiment code
(deleted by #762) and the analytics controller (#766), the worst
offenders were the MCP write tools:
- `UpdateTransaction::write` — cyclomatic complexity **20**
- `UpdateAutomationRule::write` — cyclomatic complexity **13**
Both for the same reason: a long wall of `if ($request->has('x')) {
$model->x = ...; }` blocks, one per optional field.
## What changed
Two shapes moved into `WriteTool`:
**`modelInSpace()`** — resolving a record in the space was written five
times (account, transaction, category, label, plus a rule resolver that
existed twice, once in `UpdateAutomationRule` and once in
`DeleteAutomationRule`), each a copy of the same query + null check +
message. The four public helpers are now one-liners over it, and
`ruleInSpace()` is shared instead of duplicated.
**`applyFields()`** — assigns only the fields the request actually
carries, which is the "only what you pass changes" contract these tools
document. Values are closures, so resolving a related model
(`accountInSpace`, `categoryInSpace` — either can throw a validation
error) still happens only when its field is present.
## Metrics
| | before | after |
|---|---|---|
| methods over complexity 10 | 35 | 33 |
| `UpdateTransaction::write` | 20 | 7 |
| `UpdateAutomationRule::write` | 13 | 6 |
| duplicated lines | 5.34% | 5.34% |
Duplication does not move, and it's worth being straight about why: what
jscpd still flags across `app/Mcp/Tools` is **file headers** — the `use`
block, the `#[Description]` attribute, the class line and the opening of
`schema()`. Nine near-identical lines per tool that no extraction can
remove. Deleting the duplicated `ruleInSpace` shortened
`DeleteAutomationRule` enough that its header became a clone pair with
another tool's, so the counter stayed flat while the real duplication
went away.
## Testing
`tests/Feature/Mcp` — 46 tests green, plus a new one. Nothing asserted
the resolver failure messages before, and this PR changes how they are
built (a shared template plus an optional hint), so the new test pins
both branches: the message that points at a listing tool (`Call
search_transactions to find ids.`) and the one that has no hint to
append.
## MCP Phase 2 — write tools
> **Stacked on #689** (`mcp-functionality`). Base this PR on
`mcp-functionality`, not `main`, and merge it **after** #689.
Phase 1 shipped a read-only MCP server for Pro accounts. This adds the
**write** surface and re-enables the read/read-write token scope the UI
dropped in PR1.
### Write tools
A new `WriteTool` base extends `McpTool`: on top of the Pro-plan gate it
requires the calling token to carry `mcp:write`, returning a clear error
for read-only tokens. Each concrete tool is annotated `#[IsDestructive]`
(PHP attributes aren't inherited, so the annotation lives on each tool,
not the base — a docblock on `WriteTool` notes this).
- `create_transaction` — manual (non-connected) accounts only; forces
`source = manually_created`.
- `update_transaction` / `delete_transaction` — manually-created
transactions only; bank/imported ones stay locked.
- `categorize_transaction` — sets/clears the category on **any**
transaction (imported included), marking it `category_source = manual`.
- `label_transaction` — add/remove labels on **any** transaction.
- `create_balance` — balance snapshot on manual accounts only.
- `create_category` / `update_category` / `delete_category` — mirrors
the settings controller (parent/depth/cycle rules, cashflow derivation,
child strategies).
- `create_label` / `update_label` / `delete_label`.
- `create_automation_rule` / `update_automation_rule` /
`delete_automation_rule` — JsonLogic conditions + category/label
actions, at least one action required.
- `list_labels` — a small **read** tool added so label ids are
discoverable (label/automation tools are unusable without it).
### Guardrails
Write tools never touch bank-sourced data: the existing
`TransactionSource` enum and `Account::isConnected()` are the barriers,
reused not reinvented. There is no server-side write confirmation
(client-controlled, accepted decision) — hence `#[IsDestructive]`.
### Token scope
`StoreMcpTokenRequest` re-adds `scope` (`read` | `read_write`); the
controller grants `['mcp:read']` or `['mcp:read', 'mcp:write']`. The
settings page gets its scope selector back with honest copy (new strings
added to `lang/es.json`). The `/mcp` route stays gated on
`abilities:mcp:read` — any MCP token can connect and read; the per-tool
`mcp:write` check is what blocks writes.
### Tests
Happy path + guardrail failures for every write tool, the
read-only-token rejection (via a real read-only PAT so the `tokenCan`
gate runs exactly as over HTTP), cross-user isolation, the inherited Pro
gate, and read/read_write scope validation.
### Notes
- `AutomationRule::labels()` gained a generic return annotation (needed
for larastan level 5 on the new label mapping).
### Verification
- `vendor/bin/pint --test` ✅
- `vendor/bin/phpstan analyse` (larastan level 5) — 0 errors ✅
- `php artisan test tests/Feature/Mcp
tests/Feature/Settings/McpTokenTest.php
tests/Feature/LocalizationTest.php` ✅
- `prettier --check` / `eslint` on `settings/mcp.tsx` ✅
Víctor Falcón